This section is intended to introduce the reader to various aspects of the art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Internal combustion engines are usually powered by a liquid fuel, which is stored in a tank discrete from the engine. Fuel tanks are generally sized to provide for sustained operation of the engine. For example, automobiles traditionally include fuel tanks of sufficient size to power the automobile for hundreds of miles. Accordingly, many engine or motor driven systems are equipped with fuel-monitoring systems that monitor and/or display the quantity of fuel remaining in the tank to inform the operator of the need to replenish the fuel supply before it is exhausted.
Typically, fuel-monitoring systems include a sending unit that is physically located in the fuel tank and a display unit that is located external to and, sometimes, distant from the fuel tank. The sending unit determines a level of fuel in the tank and sends an electrical signal representative of that level to the display unit, such as a gauge. In turn, the gauge visually indicates the amount of fuel remaining in the tank. For example, automobiles typically include a fuel gauge having a needle that moves between incremented “Full” and “Empty” positions on the gauge, thereby indicating the relative amount of fuel in the tank.
Traditional sending units include a float, usually made of foam, coupled to a variable resistor by a thin metal rod, generally known as a wiper. Because the float is more buoyant than the fuel, the float remains at the surface of the fuel in the tank. Accordingly, the level of fuel in the tank defines the position of the float and, in turn, the position of the wiper. The movement of the wiper along the variable resistor alters the electrical current sent to the display gauge, thereby indicating the relative level of fuel in the tank.
Unfortunately, the harsh petrochemical environment of the fuel tank may lead to malfunctions in the mechanical float and wiper assembly. Moreover, the mechanical nature of the float mechanism may also lead to inaccuracies in measuring the level of fuel in the tank. For example, the connection between the wiper and the variable resistor and/or or the top of the tank itself may limit the range of motion of the float. Accordingly, the float may be partially submerged in the fuel, so it will not begin to sink until the level of fuel in the tank reaches the bottom of the float. Thus, the sending unit will indicate a maximum or full level in the tank although a measurable amount of fuel has been consumed. In a similar manner, inaccuracies may develop when the fuel level approaches the bottom of the tank. Often, the float's range of motion does not extend to the very bottom of the tank. Accordingly, the sending unit may indicate an empty condition in the tank even though an appreciable amount of fuel remains in the tank. Moreover, the float mechanism may be affected by the orientation of the vehicle, for example if the vehicle is on a hill.
Furthermore, automobile design and construction have become increasingly complex. To increase interior space, for example, automobile designers are placing more automobile components into smaller spaces. Accordingly, to achieve maximum use of the available space and to maximize fuel tank size, fuel tanks may often be shaped to present unconventional contours. Indeed, fuel tanks may be shaped to fit around pieces of the body, frame, and/or other automobile components. Traditional sending units (i.e., those with float assemblies) may be unable to compensate for such contoured designs.